The present invention relates in general to medicine, more specifically it concerns a method for treating glaucoma.
The present invention can find application in surgery, more particularly, in neurosurgery for treating the various kinds of glaucoma.
It is known commonly that in a healthy eye a definite intraocular pressure (18 to 22 mm Hg) is constantly maintained due to a balance between the inflow and outflow of the intraocular fluid. In a glaucomatous eye circulation of the intraocular fluid is disturbed, with the result that the fluid (the so-called aqueous humour) is accumulated and the intraocular pressure starts rising. As a result, the optic nerve gradually atrophies, the blood supply of the eye is disordered, the eyesight deteriorates incessantly so that if no medical countermeasures are taken, the outcome may be complete blindness.
Traditional, classic methods of conservative and surgical treatment of open/narrow-angle glaucoma are extensively known in ophthalmologic practice to comprise medicines, i.e., in drop forms (conservative treatment) capable of reducing abnormally high intraocular pressure, surgical intervention, i.e., sclerectomy aimed at activation of uveoscleral path of outflow, including laser-aided surgery, and some other surgical operations [cf. the paper by G. G. Kornilaeva, journal xe2x80x9cVestnik oftalmologhiixe2x80x9d (Ophthalmologic Bulletin), Moscow, 1999; Collected Proceedings of the First Eurasian Conference on Ophthalmology, Ekaterinburg, 1998 (in Russian)]
Modern conservative and/or surgical treatment of glaucoma is aimed at stabilizing and reducing intraocular pressure, stopping further eyesight deterioration and atrophy of the optic nerve. In the event of progressive atrophy of the optic nerve resort is made to transcutaneous electrostimulation, repeated classic surgical intervention mentioned above, or attempts are made of surgical revascularization of optic nerve using xe2x80x9cAlloplantxe2x80x9d technique [cf. Muldashev E. R. et al., European Association for Vision, Spain, 1988; Symposium xe2x80x9cUrgent problems of Clinical Ophthalmologyxe2x80x9d, Cheliabinsk, 1999 (in Russian)]
However, despite a full complex therapy having been carried out, a certain proportion of the treated patients (20 to 30%) exhibit complete atrophy of either or both of the optic nerves and hence blindness occurs. Sometimes such a terminal stage of loss of vision is accompanied by very severe pain in one eye (more rarely in both eyes) which requires surgery for exenteration of the eyeball followed by replacing it with a prosthetic one [cf. the textbook xe2x80x9cOphthalmologyxe2x80x9d by E. I. Kovalevski, Moscow, Meditsina Publishers, 1995 (in Russian).]
One more method for treating glaucoma is known, namely, mechanical or laser-aided sclerectomy (non-penetrating deep sclerectomy). Once performed, said surgery results in restoring the natural balance of the intraocular fluid.
According to the published data, as many as one-third of a total number of the blind lost their vision due to glaucoma (cf. the textbook xe2x80x9cTolerant and Intolerant Pressure in Glaucomaxe2x80x9d, Moscow, 1991).
Etiological factors of glaucoma development are atherosclerosis and diabetes mellitus; other hereditary factors also play some part as well.
Known in the present state of the art is a method for treating glaucoma (cf. RU patent #2,021,794, C1), consisting in practicing an outflow of the aqueous humour. The surgical techniques resides in dilating the lumen of the Schlemm""s canal using a metal thread 0.05 mm thick having shape memory effect, with a view to improving the natural physiological outflow between the anterior and posterior chambers of the eye. The method in question for treating glaucoma makes no provision for neurosurgical intervention.
However, said method for treating glaucoma rarely results in completely normalizing the intraocular pressure and stabilizing the condition of the ocular fundus (that is, elimination of the glaucomatous excavation of the optic disk). Furthermore, notwithstanding the effect of stabilizing the intraocular pressure attained due to the treatment using said method, the latter fails to stabilize further atroplication of the optic nerve, nor can said method prevent further reduction of visual acuity and deterioration of the visual fields as far as complete blindness occurs. In badly neglected cases of the glaucomatous process, the transudate (i.e., the aqueous humour) pervades the oculomotor muscles and perieyeball fat. Attempts to enhance natural outflow through the Schlemm""s canal is obviously inadequate since the carrying capacity of said expanded canal is but too low due to its small area even when enlarged by said metal thread. The lesson is clear that establishing an increased intraocular outflow alone cannot arrest progressive atrophy of the optic nerve.
Hence the method for treating glaucoma discussed above fails to establish a new path for the aqueous humour to outflow outwards the eyeball with an adequate area of drainage of the aqueous humour nor can said method provide stabilization of the clinical aspect of the optic nerve atrophy or its regression followed by increasing the visual function. Ultimately, the efficacy of glaucoma treatment using the traditional methods is rather low.
It is an object of the present invention to provide a method for treating glaucoma, said method being capable of attaining, due to establishing a new path for the aqueous humour to outflow beyond the limits of the eyeball during neurosurgical intervention with an adequate area for the aqueous humour to drain off, stabilization of the clinical aspect of atrophy of the optic nerve, or regression of said atrophy, with the resultant increase in the visual function, thus adding to the efficacy of glaucoma treatment.
Said object is accomplished due to the fact that in a method for treating glaucoma consisting in outflow of the aqueous humour, according to the invention, an osteoplastic trepanation is performed in the frontal region above the affected eyeball, an extradural approach to the superior wall of the orbit is performed, while outflow of the aqueous humour is carried out by way of resection trepanation of the superior wall of the orbit in order to provide a contact between the edematous perieyeball fat and the dural surface.
It is expedient that in the event of profuse bleeding from the perieyeball fat resulting from resection trepanation of the superior orbit wall, a biological protector be positioned in the space between the superior wall of the orbit and the dura mater.
It is likewise reasonable that the aforementioned osteoplastic trepanation in the frontal region above the affected eyeball be preceded by an additional examination by way of high-resolution magnetic-resonance imaging.
The present invention allows of attaining higher treatment efficacy and makes possible curing a greater amount of patients than the traditional treating methods, this being due to the fact that despite all advances of microsurgical and pharmacological treatment methods, a certain proportion of the patients treated by the heretofore-known traditional methods cannot be cured.
The present invention enables the field of its application to be extended, since the treatment method proposed therein is applicable for treating any forms of glaucoma save the congenital one characterized by progressive atrophy of the optic nerve.
The present method for treating glaucoma is also applicable for both open-angle and narrow-angle glaucoma, as well as in bilateral glaucoma. In such a situation one-time bilateral resection of the superior wall of the orbit is indicated. Should a one time surgery be impossible for some reason, two consecutive neurosurgical interventions are performed first on the one of the orbits, then on the other, at an interval of two or three months.
Hence the present method for treating glaucoma due to the provision of a new path for the aqueous humour to flow outwards of the eyeball ensures stabilization of the clinical aspect of atrophy of the optic nerve or regression of said atrophy accompanied by increasing the visual function, which adds to the efficacy of the glaucoma treatment process.
In what follows the present invention is illustrated in some specific exemplary embodiments thereof.
The herein disclosed method for treating glaucoma consists in that an osteoplastic trepanation is performed in the frontal region above the effected eyeball and an extradural approach to the superior wall of the orbit is carried out, whereupon the aqueous humour is let to flow out beyond the limits of the eyeball. To this effect a resection trepanation of the superior wall of the orbit is performed in order to establish a contact between the edematous perieyeball fat and the dural surface. Hence said resection trepanation of the superior orbital wall established direct anastomosis between the edematous perieyeball fat that prolapses into the osseous defect and the exterior dural surface, said anastomosis establishing drainage of the excess aqueous humour which has been accumulated in the eyeball, into the dura mater and further into the venous system of the head.
Magnetic-resonance imaging of glaucoma patients revealed a pathological amplification of the increased activity signal in the orbit, more exactly, in the perieyeball fat (condition T2). The aforesaid increased activity signal gives evidence of an increased water content of the perieyeball fat. In addition, there was found a considerable increase in the diameter of the intraorbital portion of the optic nerve as far as the canalis opticus. This in turn is indicative of an edema of the optic nerve and of its being impacted in the axial occipital direction. On the healthy eye (in case of unilateral glaucoma) subjected to magnetic-resonance tomography the picture of the orbit was regarded as normal. Hence it seems that a self-impaction of the optic nerve occurs, that is, impaction of its intraorbital portion due to edema caused by disordered circulation of the aqueous humour in the eyeball. Hence an upset outflow of the aqueous humour in the eyeball results ultimately in atrophy of the optic nerve and in blindness.
The herein-proposed method for treating glaucoma is based on osteal decompression of the superior orbital wall, i.e., the roof of the orbit which also serves as the base of the anterior cranial fossa, with a view to establish immediate anastomosis between the edematous perieyeball fat and the exterior dural surface. As the dura mater possesses some resorbability it is capable of xe2x80x9creleasingxe2x80x9d the eyeball from an abnormally high water content by active water absorption. As it has been stated before in discussing the disclosed method, the treatment consists in performing a neurosurgical intervention. The surgery involves a standard osteoplastic trepanation (aimed at gaining access to the cavity of skull) in the frontal region on the side adjacent to the glaucoma-affected eyeball [cf. xe2x80x9cTextbook of Neurosurgeryxe2x80x9d by I. S. Irger, 1972, Moscow, Meditsina Publishers (in Russian)]. Thereupon, an extradural approach to the superior orbital wall is carried out, sufficient for a resection trepanation of said wall to effect, involving the backward traction towards the frontal pole. Then a standard resection trepanation is performed by making a burr hole to prevent damage to the frontal sinus, whereupon said hole is enlarged using bone nippers until a trepanation window is obtained. The overall dimensions of such a trepanation window usually measure 2.5xc3x973.0xc3x972.5 cm. As a rule, edematous fat is likely to prolapse into the thus-established trepanation defect. Finally, an osteplastic graft is laid onto site, whereupon skin stitches are applied.
In the early postoperative period, i.e., within two or three weeks after surgery, an ophthalmologic study detected disappearance of the edema or its regression (reduction), discoloration of the optic disk, reduced hyperemia of the retinal veins, and improved visual acuity by 0.05-0.1. Further observation of the ophthalmologic functions for a period of 3-6 months demonstrated at least stabilization of visual acuity and of the condition of the ocular fundus, and even the reversal of progressive changes in the ocular fundus, as well as improved visual acuity. In a control magnetic-resonance imaging of the orbit involving displaying the optic nerve there is observed reduction of absolute values of the increased activity signal (in T2 condition) from the perieyeball fat, restoring normal diameter of the intraocular optic nerve portion comparable with the diameter of the contralateral nerve.
In the case of post-decompression situation of the superior orbital wall following surgery for resection trepanation of said orbital wall and when profuse bleeding from the prolapsing perieyeball fat is observed, a biological protector is made use of, to be placed in the space between the superior wall of the orbit and the dura mater. Used as said protector may be the commonly known hemostatic sponge (cf. the journal xe2x80x9cNeurosurgeryxe2x80x9d, June 1996, vol.38 #6, Williams and Wilkins, pp.6-15), or a tachocomb [cf. xe2x80x9cLesion of the Brainxe2x80x9d, in: Proceedings of the Fifth International Symposium held in Saint-Petersburg, 1999, p.486 (in Russian)]. Furthermore, with a view to assessing the status of the perieyeball fat and the diameter of the optic nerve, prior to performing the aforesaid osteoplastic trepanation in the frontal region above the affected eyeball an additional examination is carried out in the form of a standard magnetic-resonance imaging.
The present method of treating glaucoma was tested under clinical conditions. Clinical trials were conducted at the neurological and neurosurgical clinic xe2x80x9cNeuroaesculapxe2x80x9d in Moscow for treating patients with the various forms of glaucoma.
Given below are some examples illustrating the present method of neurosurgical treatment of glaucoma.